Various cardiovascular, neurosurgical, pulmonary and other interventional procedures, including repair or replacement of aortic, mitral and other heart valves, repair of septal defects, pulmonary thrombectomy, coronary artery bypass grafting, angioplasty, atherectomy, treatment of aneurysms, electrophysiological mapping and ablation, and neurovascular procedures, may require general anesthesia, cardiopulmonary bypass, and arrest of cardiac function. In such procedures, the heart and coronary blood vessels must be isolated from the remainder of the circulatory system. This serves several purposes. First, such isolation facilitates infusion of cardioplegic fluid into the coronary arteries in order to perfuse the myocardium and thereby arrest cardiac function, without allowing the cardioplegic fluid to be distributed elsewhere in the patient's circulatory system. Second, such isolation facilitates the use of a cardiopulmonary bypass system to maintain circulation of oxygenated blood throughout the circulatory system while the heart is stopped, without allowing such blood to reach the coronary arteries which might resuscitate the heart. Third, in cardiac procedures, such isolation creates a working space into which the flow of blood and other fluids can be controlled or prevented so as to create an optimum surgical environment.
Using current techniques, isolation of the heart and coronary blood vessels is accomplished by placing a mechanical cross-clamp externally on the ascending aorta downstream of the ostia of the coronary arteries, but upstream of the brachiocephalic artery, so as to allow oxygenated blood from the cardiopulmonary bypass system to reach the arms, neck, head, and remainder of the body. A catheter is then inserted directly into the ascending aorta between the cross-clamp and the aortic valve, and cardioplegic fluid is infused through the catheter into the ascending aorta and coronary arteries to perfuse the myocardium. An additional catheter may be introduced into the coronary sinus for retrograde perfusion of the myocardium with cardioplegic fluid. In addition, the myocardium is usually cooled by irrigating with cold saline solution and/or application of ice or cold packs to the myocardial tissue. Cardiac contractions will then cease.
Known techniques for performing major surgeries such as coronary artery bypass grafting and heart valve repair and replacement have generally required open access to the thoracic cavity through a large open wound, known as a thoracotomy. Typically, the sternum is cut longitudinally (a median sternotomy), providing access between opposing halves of the anterior portion of the rib cage to the heart and other thoracic vessels and organs. An alternate method of entering the chest is via a lateral thoracotomy, in which an incision, typically 10 cm to 20 cm in length, is made between two ribs. A portion of one or more ribs may be permanently removed to optimize access.
In procedures requiring a median sternotomy or other type of thoracotomy, the ascending aorta is readily accessible for placement of an external cross-clamp through this large opening in the chest. However, such surgery often entails weeks of hospitalization and months of recuperation time, in addition to the pain and trauma suffered by the patient. Moreover, while the average mortality rate associated with this type of procedure is about two to fifteen per cent for first-time surgery, mortality and morbidity are significantly increased for reoperation. Further, significant complications may result from such procedures. For example, application of an external cross-clamp to a calcified or atheromatous aorta may cause the of release of emboli into the brachiocephalic, carotid or subclavian arteries with serious consequences such as strokes. In up to 6% of the open-chest coronary bypass surgeries performed in the United States, there is noticeable mental deterioration which is commonly attributed to cerebral arterial blockage from emboli released during the bypass procedure.
Methods and devices are therefore needed for isolating the heart and coronary arteries from the remainder of the arterial system, arresting cardiac function and establishing cardiopulmonary bypass without the open-chest access provided by a median sternotomy or other type of thoracotomy. Further, the methods and devices should facilitate such isolation of the heart and coronary arteries without the high risk of embolus production associated with external aortic cross-clamps.
Of particular interest to the present invention is the treatment of heart valve disease. There are two major categories of heart valve disease, namely, stenosis, which is an obstruction to forward blood flow caused by a heart valve, and regurgitation, which is the retrograde leakage of blood through a heart valve.
When it is necessary to repair or replace a malfunctioning heart valve within a patient, heretofore the repair or replacement has been accomplished by a major open-heart surgical procedure, requiring general anesthesia and full cardiopulmonary by-pass with complete cessation of cardiopulmonary activity. While the use of extracorporeal cardiopulmonary by-pass for cardiac support has become well established, this use has involved median sternotomy or less commonly thoracotomy with all of the trauma that necessarily accompanies such a major surgical procedure. Such surgery usually includes one to two weeks of hospitalization and months of recuperation time for the patient. The average mortality rate with this type of procedure is about five to six percent, and the complication rate is substantially higher. Descriptions of open-heart procedures for replacing heart valves can be found in Gibbon's Surgery of the Chest, 5th Ed., David C. Sabiston, Jr., M.D., Frank D. Spencer, M.D., 1990, Vol. II, Ch. 52, pp. 1566-1596, and Textbook of Interventional Cardiology, Eric J. Topol, 1990, Chs. 43-44, pp 831-867.
Endovascular surgical procedures on the heart have been developed recently which, in contrast to open-heart surgical procedures, may have a reduced mortality rate, may require only local anesthesia, and may necessitate only a few days of hospitalization. However, the range of applications of endovascular heart procedures other than those of the coronary arteries, such as angioplasty and atherectomy, has been limited.
Some progress has been made in developing endovascular procedures involving the heart valves. For example, for patients with severe stenotic valve disease, who are too compromised to tolerate open-heart surgery to replace the heart valve as described above, surgeons have attempted endovascular balloon aortic or mitral valvuloplasty. These procedures involve endovascularly advancing a balloon dilatation catheter into the patient's vasculature until the balloon of the catheter is positioned between the valve leaflets and then inflating the balloon to split the commissures in a diseased valve with commissural fusion and to crack calcific plaques in a calcified stenotic valve. However, this method may provide only partial and temporary relief for a patient with a stenotic valve. The rapid restenosis and high mortality following balloon aortic valvuloplasty has led to virtual abandonment of this procedure as a treatment of the diseased aortic valve.
An endovascular treatment regimen for regurgitant heart valves, which involves valve supplantation, has been disclosed in the patent literature, but apparently the procedure has not been clinically practiced. In this procedure, it is conceived that an elongated catheter is used to insert a mechanical valve into the lumen of the aorta via entry through a distal artery, for example, the brachial or femoral artery. One such mechanical valve is described in U.S. Pat. No. 4,056,854 (Boretos et al.) that is designed to be positioned against the artery wall during forward flow, as compared to the mid-center position of the valve described in U.S. Pat. No. 3,671,979 (Moulopoulos). The valve positioned against the arterial wall is intended to reduce the stagnation of blood flow and consequent thrombus and emboli formation compared to a valve at mid-center position. The mechanical valves previously described require an elongated mounting catheter extending out of the arterial entry point to maintain the position of the valve in the descending aorta. These valves would be expected to present several problems. The valves do not provide a permanent or internalized system. Furthermore, since both involve a mechanical valve, which predisposes the patient to thrombus formation and emboli, long term anticoagulant therapy is required. A serious complication of long term anticoagulant therapy is intracranial hemorrhage. Finally, the supplemental valve is placed downstream from both the normal valve position and the coronary ostia, so normal heart and coronary artery hemodynamics are not restored.
Of additional interest to the invention are techniques for establishing cardiopulmonary bypass and for performing interventional procedures in the heart and great vessels which minimize trauma and risk of complications resulting from vascular penetrations, whether percutaneous punctures or surgical cut-downs. To establish cardiopulmonary bypass according to conventional techniques, a venous cannula is introduced into a major vein such as the inferior vena cava, or into the heart itself, to withdraw deoxygenated blood from the patient and deliver the deoxygenated blood to a CPB system for oxygenation. An arterial cannula is introduced into a major artery such as the aorta, an iliac artery, or a femoral artery, for delivering oxygenated blood from the CPB system to the patient's arterial system.
For endovascular procedures such as angioplasty, atherectomy, valvuloplasty, cardiac mapping and ablation, and the like, interventional devices are introduced into a peripheral artery and transluminally positioned at the treatment site where the procedure is performed. For example, in angioplasty or atherectomy, a catheter is introduced into a femoral artery and advanced through the aorta into a coronary artery to treat an occluded region therein. In some circumstances, the use of CPB may be desirable during such procedures. If CPB is utilized during these procedures, the arterial and venous CPB cannulae are usually introduced into a femoral artery and femoral vein, respectively, by means of a surgical cut-down in the groin area on one side of a patient's body. The endovascular interventional devices may then be introduced into a femoral artery in the groin area on the other side of the patient's body.
In order to minimize trauma and the risk of complications such as infection, it is generally desirable to minimize the number of vascular penetrations or "sticks" which are made in a patient during a procedure. Such penetrations are a significant cause of morbidity and mortality in cardiac procedures. The risks are greater where the penetrations are either surgical cut-downs or large percutaneous penetrations, as are usually required for introduction of venous and arterial CPB cannulae and for some types of endovascular interventional devices. The risks are particularly high when such penetrations are made on arterial vessels.
Moreover, in some cases, one or more of a patient's femoral arteries, femoral veins, or other vessels for arterial and venous access may not be available for introduction of cannulae, due to inadequate vessel diameter, vessel stenosis, vascular injury, or other conditions. In such cases, there may not be sufficient arterial and venous access to permit the use of femoral arterial and venous CPB cannulae as well as other interventional devices, such as an angioplasty catheter, atherectomy catheter or other device, introduced through a femoral vein or artery contemporaneously as part of a single surgical procedure. Therefore, unless alternate arterial or venous access for one or more of these catheters can be found, the procedure cannot be performed using endovascular techniques.
What have been needed and heretofore unavailable are methods and systems for satisfactorily performing various cardiovascular procedures, particularly procedures for heart valve placement or removal and replacement, which do not require a thoracotomy. Improved methods and devices are also needed for establishing CPB and performing interventional procedures that reduce the number of arterial and venous penetrations required for CPB cannulae and other endovascular devices. The methods and devices will preferably facilitate isolating the heart and coronary arteries from the remainder of the arterial system, arresting cardiac function, and establishing cardiopulmonary bypass without the open-chest access provided by a thoracotomy. The methods and devices should minimize the number of arterial and venous penetrations required in such closed-chest procedures, and desirably, should require no more than one femoral arterial penetration and one femoral venous penetration. In addition to procedures requiring arrest of cardiac function, the methods and devices should be useful for a variety of closed-chest interventional procedures that require the use of cardiopulmonary bypass, even where cardiac function is not arrested. The present invention satisfies these and other needs.
The descriptive terms downstream and upstream, when used herein in relation to the patient's vasculature, refer to the direction of blood flow and the direction opposite that of blood flow, respectively. In the arterial system, downstream refers to the direction further from the heart, while upstream refers to the direction closer to the heart. The terms proximal and distal, when used herein in relation to instruments used in the procedure, refer to directions closer to and farther away from the operator performing the procedure.